1. Field of the Invention
The present invention relates to a noise canceling technique in voice input to an electronic apparatus such as a personal computer.
2. Description of the Related Art
In recent years, portable electronic apparatuses such as notebook personal computers and personal digital assistants (PDAs) have become popular. In some electronic apparatuses of this type, a rectangular display screen exposed on the front surface of the display can be utilized in both the portrait and landscape directions.
Most electronic apparatuses of this type have a sound function such as a voice input function via a microphone or a voice output function via a loudspeaker. These days, electronic apparatuses having an advanced voice input function of canceling noise by using two microphones are becoming available. The method of canceling noise by using two microphones is called a microphone array system. Two microphones are set so that they are located at the two base vertices of an isosceles triangle virtually drawn using a sound source as the upper vertex. Of sounds input from the two microphones, a sound with a larger difference in volume level between the sounds is removed as noise. By using the microphone array system, only the user's voice can be very clearly picked up even when the electronic apparatus is used in a slightly noisy environment.
As a method of acquiring a desired sound, which is different from the microphone array system for canceling noise, there is proposed a method of two-dimensionally arraying a plurality of microphones and properly selecting acoustic signals output from the microphones (see, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2002-165292).
As described above, when noise canceling of the microphone array system is applied to an electronic apparatus, the installation locations of two microphones on a housing must be considered so that the two microphones are located at the two base vertices of an isosceles triangle using the mouth of the user as the upper vertex. In an electronic apparatus with a display screen exposed on the front surface of the display, two microphones are preferably set near, e.g., the bottom of the display screen so as to be spaced apart from each other by the same distance from the vertical center line of the display screen.
However, in an electronic apparatus whose rectangular display screen can be utilized in both the portrait and landscape directions, two microphones are vertically arranged one above the other near the left or right side of the display screen depending on the orientation of the display screen. No isosceles triangle using the mouth of the user as the upper vertex is formed, and thus noise canceling malfunctions.
According to the method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-165292, the user only appropriately selects one of scattered microphones. This method cannot solve the above-mentioned problems.